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Tham khảo tài liệu 'vehicular technologies increasing connectivity part 11', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Correlation Coefficients of Received Signal I and Q Components 291 0.3 0.3 0 0.1 0.2 Ăfơ 0.1 J 0.2 3 0.3 0.87 0.7 0 y 7 -0 0.3 0.2 p 0.1 c Locus of theory fine simulation solid Fig. 7. Correlation coefficient in a domain with time and frequency axes Type 1 exponential distribution K -TO dB 292 Vehicular Technologies Increasing Connectivity correlation for K -TO dB is slightly lower than the theoretical one. We suppose that the difference is due to different conditions between the theoretical and simulation models for the delay profile such as the number of waves N and the counted effective amplitude in hi. Therefore we repeated the simulation changing from N 10 and effective amplitude of -20 dB to N 100 and effective amplitude of less than -50 dB. As a result the correlation became close to the theoretical one. The above results show that the autocorrelation is independent of the K factor while the frequency correlation depends on the K factor. The correlation coefficient in a domain with time and frequency axes for NLOS is shown in Fig. 7. Figure 7 a is a bird s-eye view of pAx obtained from 13 which makes it easy to comprehend the overall pAx . We can see that pAx has a peak p 0 1 at the origin Ax 0 and that pAx becomes smaller with increasing Ax or as fmTs and Afơ become larger. Furthermore pAx decreases in a fluctuating manner on the time axis but decreases monotonically on the frequency axis. The high area of pAx needed to allocate the pilot signal in coherent detection such as pAx 0.8 is very small in the domain whereas the low area needed to design the diversity antenna such as pAx 0.5 is spread out widely. Figure 7 b also shows a bird s-eye view of the simulated correlation Figs. 7 a and b both exhibit almost the same features. Figure 7 c shows the loci of the theoretical and simulated correlations in a small area up to 0.3 on both axes with contour lines of pAx . It is easy to compare them. The theoretical value on the time axis agrees well with the .
